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Delta-T-lymphocytosis in a patient with thymoma
M Lishner1, M Ravid, J Shapira
1Department of Medicine, Sackler Faculty of Medicine, Tel Aviv University, Israel.
Background:
Malignant thymoma is composed of neoplastic epithelial cells and small lymphocytes. Rarely, patients also may have peripheral T-lymphocytosis. These lymphocytes have been considered nonneoplastic because of their microscopic appearance and immunophenotype, as well as gene rearrangement studies.
Methods:
A 42-year-old man developed lymphocytosis 3 years after the completion of intensive combined chemoradiotherapy protocol for lymphocytic thymoma. These peripheral blood lymphocytes were evaluated phenotypically and genotypically.
Results:
Immunophenotyping established that the cells were CD3 positive, CD4 negative, CD8 negative, T-cell receptor (TCR)-alpha/beta negative, and TCR-gamma/delta positive. Gene rearrangement studies with TCR-delta probe confirmed the monoclonality of these cells. Chromosome analysis showed deletion of chromosome Y. The clinical course was progressive and had the features of malignant lymphoma.
Conclusions:
To the authors' knowledge, this is the first report of a patient with thymoma in whom monoclonal proliferation of T-gamma/delta peripheral blood lymphocytes was confirmed immunophenotypically and genotypically. These monoclonal TCR-gamma/delta lymphocytes may belong to the malignant clone of the thymoma; however, the possibility that they represent an evolution of a second lymphatic malignancy cannot be excluded.